It has been more than 100 days since the shootings at Sandy Hook Elementary School. Since then, leaders in Washington have talked a lot about gun violence, but they have not passed a bill. Today, gun control advocates tried to give the process a jolt. They planned events around the country for what they called a national day of action. And as NPR's Ari Shapiro reports, President Obama joined in.

ARI SHAPIRO, BYLINE: In the East Room of the White House, the president and vice president stood before two rows of mothers.

PRESIDENT BARACK OBAMA: We have moms on this stage whose children were killed as recently as 35 days ago.

SHAPIRO: Ever since the Newtown shootings in December, the White House has pushed for a gun bill. The momentum seems to have slowed, though. At this point, few people believe an assault weapons ban will pass. A limit on high-capacity magazines looks out of reach too. Expanded background checks once seemed like a consensus measure, and now passage appears to be a real challenge. But President Obama said there is still a huge opportunity here.

OBAMA: This is our best chance in more than a decade to take common-sense steps that will save lives.

SHAPIRO: The Senate Judiciary Committee has passed bills to expand background checks, boost school safety and crack down on people who buy guns for criminals. But a vote in the full Senate will be harder. Republicans are likely to filibuster the bills. The president said these measures are supported by an overwhelming majority of Americans, and as he so often does, he asked people listening to speak up.

OBAMA: And I ask every American to find out where your member of Congress stands on these ideas. If they're not part of that 90 percent who agree that we should make it harder for a criminal or somebody with a severe mental illness to buy a gun, then you should ask them, why not? Why are you part of the 10 percent?

SHAPIRO: Those members of Congress are almost all at home this week on Easter recess. And in state capitals, there's actually been far more action on guns than there's been in Washington. Ilya Shapiro is with the libertarian Cato Institute.

ILYA SHAPIRO: National political reporters, by definition, are based in Washington covering what's on Congress. That's what gets on the national news. But a lot of action is going in the states.

SHAPIRO: New York and Colorado moved much faster than the federal government. They passed measures ranging from expanded background checks to limits on high-capacity magazines. Maryland and Connecticut both look close to passing such measures too.

But even in states where it looks favorable, the lobbying is heavy. Last week, The Huffington Post obtained this National Rifle Association robocall pushing the NRA message in Connecticut.

(SOUNDBITE OF ROBOCALL)

UNIDENTIFIED MAN: Anti-gun legislators are aggressively pursuing numerous proposals that are designed to disarm and punish law-abiding gun owners and sportsmen.

SHAPIRO: The group Mayors Against Illegal Guns released its first TV ad featuring Newtown family members today. It's airing in Connecticut, pushing state lawmakers to tighten gun rules there.

(SOUNDBITE OF TV AD)

GILLES ROUSSEAU: She just wanted to teach little kids, and that was her goal, and she died doing it.

SHAPIRO: Many states are moving in a direction the president would not like. In Pennsylvania, state Representative Daryl Metcalfe has a bill to prohibit enforcement of any new federal gun restrictions.

STATE REPRESENTATIVE DARYL METCALFE: It's important that we ensure that the federal government knows that Pennsylvanians will not tolerate any future erosion or any more erosion of their right to bear arms.

SHAPIRO: According to the National Conference of State Legislatures, 28 states are considering similar measures to block new federal gun laws. Given that so much of the action on guns right now is at the state level, White House spokesman Josh Earnest says President Obama is looking beyond Washington too.

JOSH EARNEST: This is one of the reasons that we're going to Colorado to talk to law enforcement officials and other elected officials in Colorado who have recently taken steps that would make their community safer there.

SHAPIRO: The president will make that trip to Denver next Wednesday. Ari Shapiro, NPR News, the White House. Transcript provided by NPR, Copyright NPR.